How to get sharper shadows out of an HDRI
Here is a thread over on blender Artists, maybe this helps

https://blenderartists.org/t/how-to-setup-a-hdri-to-get-sharp-shadows/578712/24

or you can use this blogposts by Greg Zaal with a lot of helpful Information
http://blog.gregzaal.com/2016/02/23/what-makes-good-hdri/

http://blog.gregzaal.com/2013/07/24/cif-2-hdr-lighting/